If you want to keep any data secret, preferable within your handheld PC, CipherCE is the right choice to have that. It is designed to be as convenient as safe.
Cipher.exe is a small program, with which you can
compress and
encrypt
any file with
any passphrase.
You can also
decrypt and
uncompress
the file
with the right password
and edit it with the associated application,
before it will be encrypted again automagically.